docs: def push_pos(self, *args):
          """Set my current position, expressed as proportions of the board's
          width and height, into the ``_x`` and ``_y`` keys of the
          entity in my ``proxy`` property, such that it will be
          recorded in the database.
  
          """
          self.proxy['_x'] = self.x / self.board.width
          self.proxy['_y'] = self.y / self.board.height